Obstructive sleep apnea, excessive daytime sleepiness, and adherence to antihypertensive treatment: Questionnaire survey

To the Editor

I read with interest the article by Righi and colleagues.1 The authors conducted a cross‐sectional study to investiage the association between obstructive sleep apnea (OSA), excessive daytime sleepiness, and adherence to antihypertensive treatment in 416 patients with hypertension. OSA and sleepiness were judged by the STOP‐Bang questionnaire and Epworth Sleepiness Scale, respectively. By Poisson regression analysis, prevalence ratios (95% confidence intervals) of OSA and sleepiness for nonadherence medication were 2.31 (1.10–4.90) and 1.69 (1.11–2.56), respectively. I have two concerns about their study.

First, the prevalence of OSA is high in adults.2 Sleep polysomnography is a gold standard to determine OSA, but a simple screening tool by questionnaire is important to identify patients with OSA to avoid time‐consuming and financial costs. Among several questionnaires for OSA, the STOP‐Bang questionnaire has been frequently used.2, 3 The STOP‐Bang questionnaire consists of 8 items on snoring (S), tiredness (T), observed apneas (O), high blood pressure (P), increased body mass index (B), age (a), neck circumference (n), and male sex (g). The binary response to each item was scored as 1 or 0, and each item score was added to obtain the total score.4 Among 8 items on the STOP‐Bang questionnaire, items 1 and 3 present a difficulty in appropriate response because of the content of the questionnaire as follows.

Item 1: Do you snore loudly (louder than talking or loud enough to be heard through closed doors)?

Item 3: Has anyone observed you stop breathing during your sleep?

I previously applied the STOP‐Bang questionnaire to 447 industrial office workers (345 men and 102 women) with a mean age (standard deviation) of 40.5 (9.0). Regarding item 1, the number of responses of “Yes,” “No,” and “Not determined” were 73 (3), 118 (58), and 153 (41) in men (women). Regarding item 3, the number of responses of “Yes,” “No,” and “Not determined” were 56 (3), 148 (64), and 141 (35) in men (women). These data reveal that the determinations on snoring and stopped breathing during sleep are sometimes difficult to assess by self‐administered questionnaire. If the missing data are considered as “Yes” or “No,” overestimation or underestimation occurs for the screening of OSA. The responses to items 1 and 3 are fundamentally important for the validity of the STOP‐Bang questionnaire, although there have been no discussions on the lack of response in each item.5, 6 Righi and colleagues used data from patients with hypertension and did not consider the item “high blood pressure.” In addition, they adopted three or more positive items of the STOP‐Bang questionnaire as patients at high risk for OSA. Taken together, the cutoff point for screening OSA should be handled with caution.

Second, Zhou and colleagues7 reviewed the relationship between neurocognitive function and excessive daytime sleepiness in patients with OSA. They concluded that excessive daytime sleepiness possibly relates to the domain and extent of cognitive impairments in patients with OSA, and there was no improvement of cognitive deficits by continuous positive airway pressure therapy. I speculate that medication nonadherence would be partly related to the level of cognition. Because the causal association cannot be confirmed by a cross‐sectional study, the effect of OSA and excessive daytime sleepiness on subsequent adherence to antihypertensive treatment should be conducted via a prospective study by considering the level of cognition.